Which way would an alpha particle go if deflected by charged plates?

Alpha particles consist of two protons and two neutrons, so they have a positive charge. Therefore they will be attracted towards a negative plate, and repelled from the positive. This is a fairly common method for determining the mass to charge ratio of particles, because the angle of deflection is related to charge/mass. An electron for instance would be attracted to a positive plate, and it would be deflected much more strongly since its charge/mass ratio is much higher.